Wonderful.
No dangerous permissions.
I use it by clicking the star.
Then "dupes".
Then "mark all but first in each group".
Then, optionally, if I don't want it to touch some folders, f.e. SessionSync, I click "Select a folder to get ...".
Then "Unmark all from selected folder".
Optionally, repeat the last two steps.
Finally, I click "Remove marked bookmarks."

Thanks a lot for this :)